1. Technical Field
The embodiments described and claimed herein relate generally to wheelchair securement methods, systems, and devices for vehicles.
2. Background Art
Traditionally, two different types of tie-down assemblies (also referred to as tie-downs), have been used to secure a wheelchair inside a vehicle: refractor type tie-downs and manual belt type tie-downs. Both of these types of tie-downs are briefly discussed below, along with their drawbacks.
Refractor type tie-downs are often limited by the strength or material of the restraint being used, and are limited in the way they are currently designed because only one length of the restraint is used when securing the wheelchair. Because of these limitations, the majority of refractors are generally limited to securing a wheelchair having a mass of a 100-120 kg when using two refractors in the rear of the wheelchair. If a wheelchair above these limits is to be secured, three or more retractor tie-downs are required in the rear of the securement area. If the restraint strength is increased, the restraint generally becomes thicker and this means the refractor needs to increase in size to house this restraint (which makes them heavier and more difficult to install or use) or the amount of restraint available is significantly reduced, reducing their reach and limiting their use to very small vehicle installations. In such a scenario, the only way to secure heavy wheelchairs is to use more than two refractors. The disadvantages of using more than two refractors include more clutter on the vehicle floor, which could also result in other passengers tripping over the clutter, additional installation of more tie-downs, which results in more time and cost, improper use of the retractors as it requires drivers or operators to discern when to use multiple refractors on wheelchairs of certain weights, and the arrangement of using more than two refractors is not aesthetically pleasing.
Manual belt type tie-downs are often stronger than the refractor type as the design allows the restraint to be doubled, and as a result they can often secure wheelchairs up to a mass of around 140 kg using two tie-downs in the rear of the location. If a wheelchair above these limits is to be secured, three or more tie-downs are required. Manual tie-downs require more technical operation in order to properly secure a wheelchair as the operator must perform additional steps of adjusting, tightening and locking the restraint, and storing the excess restraint. Tightening of the manual tie-downs require the use of an over-center buckle, ratchet, or similar mechanism which requires two hands and considerable effort, which may, at times, prove to be difficult for many individuals. As such, manual tie-downs are considered more cumbersome to use with the increased risk of improper use, and are, therefore, generally not favored. Further, they are less compact than retractors and take up more storage room. Also, where the vehicle footprint is small and/or the wheelchair tie-down securing locations are low, these tie-downs often need to be very short in length and the minimum length for these systems are inhibited by the buckle or adjuster mechanism from being reduced further in length. When wheelchairs exceeding 140 kg are used, currently three or more tie-downs are required. As noted above, using more tie-downs can lead to increased clutter, misuse, and increased installation costs.
There is a growing concern that wheelchairs are increasing in mass and size, while restraints, tie-downs, and/or securement systems used to secure such wheelchairs have not been properly designed or tested with these larger wheelchairs in mind. For example, some powered wheelchairs can have a mass as high as 200 kilograms (kg), and as a result, standard testing procedures for wheelchair restraints using an 85 kg surrogate wheelchair are not representative of the actual wheelchair masses that may be used in the market.
In addition to the increase in size and mass of wheelchairs in recent years, vehicles are also becoming smaller. As such, the environment and space for securing wheelchairs in these kinds of vehicles is becoming ever more challenging. Personal wheelchair accessible vehicles are often designed to carry one or two wheelchairs, with one sitting behind the other. Fitting the wheelchair into these vehicles often requires the wheelchair to sit on a 10 degree slope, or require that the tie-downs angles used to secure a given wheelchair are set very steep to fit within the space.
To explain by way of an example, standards such as the ISO10542 recommend a maximum rear tie-down angle of 45 degrees. In reality though, the rear tie-down angles are often at 50-55 degrees. This type of geometry can significantly increase the loading in the rear tie-downs, which means that often times, even with a 85 kg wheelchair, current refractor tie-down technology is not suitable or strong enough to work in this environment. The only options available in such a scenario are to revert to a manual belt type tie-down (which are slightly stronger) or modify the vehicle layout which is both time consuming and very costly.
Further, if a heavy wheelchair is to be secured in a small vehicle, then there is often insufficient room to install more than two tie-downs. Often, in these situations the rear tie-downs from the front wheelchair position clash with the front tie-downs from the rear wheelchair positions. This results in either the comfort of the wheelchair passenger being compromised or having to utilize costly vehicle conversions, for example by installing the tie-down refractors under the vehicle floor.
In view of these market changes (e.g., introduction and use of heavier wheelchairs and smaller vehicles), there is an increased demand for tie-downs to be tested with heavier wheelchairs, and a push that standards declare the maximum wheelchair mass that a restraint can secure. An example of such a standard is the UK PAS 2012. When tested to such standard, traditional refractor tie-downs are limited to securing a wheelchair of mass of around 100-120 kg and a belt type tie-down of around 140 kg. If a wheelchair above these limits is to be secured, three or more tie-downs are required in the rear.
Accordingly, there is a need for stronger ‘heavy duty’ securement systems that can be used to secure heavier wheelchairs in smaller vehicles having limited or challenging installation space, and that be used to reduce the number of tie-down assemblies for securing such wheelchairs.